Starting switch for electrical discharge lamps



Aug. 29, 1944. L BETZ 2,356,812 7 STARTING SWITCH FOR ELECTRICAL DISCHARGE LAMPS Filed Feb. 21. 1942 Patented Aug. 29, 1944 STARTING swrrcn FOR. ELEUIRIGAL DISCHARGE LAMPS Paul L. Betz, Baltimore, Md., assignor to Consolidated Gas Electric Li of Baltimore, Maryland ght and Power Company Baltimore Md a. corporation of Application February 21, 1942, Serial No. 431,893 19 Claims. (01. 315-100) This invention relates to starting switches for electrical discharge lamps, such as fluorescent lamps, and more particularly to starting switches which are so constructed that the starting operations of the switch are discontinued automatically if the lamp is defective or otherwise unable to maintain the electrical discharge.

Generally stated, an electrical discharge lamp comprises a pair of spaced electrodes in an envelope containing a gas or mixture of gases at a suitable pressure. The electrodes are adapted to be heated to incandescence by passage of an electric current therethrough, and are in circuit with a starting switch whose function is to momentarily connect said electrodes in series to bring them to incandescence and then interrupt the circuit transient voltage, due to the presence of a re-' actor in another part of the circuit, initiates. a discharge within the lamp.

As the lamp approaches the end of its useful life, the decrease of electron emission from the electrodes makes the starting of the lamp more and more difiicult, until a point is finally reached at which it is impossible to maintain the electrical discharge. Thereafter, upon energizing the lamp, the starting switch continues to go through the cycle of starting operations above referred to, successively making and breaking the filamentheating circuit, and if the lamp fails to start, this continued operation of the starting switch may result in damage to the switch itself or to the transformer or to the reactor associated therewith.

It is an object of the present invention to provide a starting switch for electrical discharge lamps with means whereby, after a limited number of unsuccessful attempts to start a lamp, the starting operation is discontinued automatically,

A further object of the present invention is to provide a starting switch of the character referred to with means for discontinuing the starting operation of the switch under abnormal conditions'and which, upon deenergizat-ion, is automatically restored to a condition for normal operation.

Another object of this invention is to provide a starting switch for electrical discharge lamps with safety means which discontinues the operatiorr of the starting switch if, after a predeter- I mined'number of cycles, the lamp fails to start.

Another object of this invention'is to provide a'startin'g switch of the character referred to with' a thermally operated switch which is northrough the electrodes, whereupon the resultant v tact 23 for co-operation with the contact 25. Also mally inoperative to interrupt the circuit but which, under abnormal conditions, is opened to interrupt the starting circuit.

Another object of this invention is to provide a starting switch as last characterized with means for maintaining the switch in said open position as long as the starting circuit is energized.

Another object of this invention is to provide a starting switch for electrical discharge lamps which fulfills the foregoing objects and which at the same time is of such simplicity that it may be readily embodied in commercial starting switches for electrical discharge lamps without unduly complicating the circuit arrangements or the associated structure.

Other objects of the invention will appear as the description of the invention proceeds.

The invention is capable of receiving a variety of mechanical expressions, two of which are illustrated on the accompanying drawing, but it is to be expressly understood that the drawings are for purposes of illustration only, and are not to be construed as a definition of the limits of the invention, reference being had to the appended claims for that purpose.

In the drawing, Figs. 1 and 2, respectively, 11- lustrate diagrammatically circuit arrangements for starting switches for electrical discharge lamps embodying the present invention.

In the embodiment of Fig. 1 an electrical discharge lamp, as a fluorescent lamp, is diagrammatically indicated at In, the same having filamentary electrodes H and I2, respectively, connected through wires l3 and It to the terminals of a transformer I 5 having an input represented by the leads I6. In series with the transformer l5 and the electrodes is a suitable reactor I! for initiating the discharge in the lamp in accordance with principles well understood in the art. The electrodes H and i2 are also in series through wires [8 and I9, respectively, with the terminals '20 and 2| of the starting switch now to be described. v

The improved starting switch embodying the present invention is connected with said terminals 20 and 2!. Connected with terminal 20 through wire 22 is a bimetallic contact arm 23 provided with contacts 24 and 25. A second bimetallic contact arm 26 is provided with a contact 21 for co-operation with the contact 24 and' a third bimetallic contact arm 28 is provided. with a conconnected to the terminal 20 in parallel with the wire 22 is a suitable resistor 30 constituting a heating element in heat interchanging relationship with the contact arm 23, said heating element 30 being connected to a wire 3| to which is connected wire 32 from the contact arm 26. Wire 32 includes a relatively small resistor 33, or in place of using a separate resistor 33, the material of the contact 21 may be such as to provide the necessary resistance in series with the arm 26. Another resistor 34 is connected in series with the contact arm 28, and constitutes a heater in heat interchanging relation with arm 28, being shown as surrounding the arm 28. Re sistor 34 is connected to the wire 3| by wire 35. Contact arm 28 also has suitably formed thereon or attached thereto a finger 36 for a purpose to be described.

Wire 3| is connected to a bimetallic contact arm 31 carrying a contact 38 in position to cooperate with a contact 39 on a bimetallic contact arm 48. Contact arm 40 is connected to the terminal 2| by wire 4|. Connected in shunt around the contact arms 31 and 49, and their contacts 38 and 39 is a resistor 42 constituting a heating element in heat interchanging relationship with the contact arm 49, said resistor 42 being connected to the wire 3| by wire 43and to the lead wire by wire 44. l

A condenser 45 is connected between the terminals 28 and 2| by a connection 46 to wire 22 and a connection 41 to wire 4|, whereby said condenser is electrically in parallel with the other circuits of the starting switch and. functions to absorb energy incident to the separation of the contacts of the starting switch as understood in the art.

When the lamp is deenergized the several contacts above referred to are in the relative positions shown in Fig. 1, i. e., the circuit is open between contacts and 29 but closed at contacts 24, 21 and at contacts 38, 39. Upon supplying energy at the input I 6 to transformer I5 the current flows through the circuit consisting of reactor wire l3, electrode wire l8, terminal 28, wire 22, bimetallic contact arm 23, contacts 24, 21, bimetallic contact arm 26, resistor 33, wires 32 and 3|, bimetallic contact arm 31, contacts 38, 39, bimetallic contact arm 40, wire 4|, terminal 2|, wire |9, electrode l2 and wire l4 to the opposite side of the transformer l5. A portion of the current is also shunted through the parallel circuit including heater element and its connecting wire 3|. Upon energizing the circuits as above referred to, heat from heater 38 and heater 33 causes contact arm 23 to flex and open the circuit between contacts 24 and 21. This interrupts the current flowing through the above described circuit including the incandescent lamp electrodes and I2. and gives rise to a transient voltage across the electrodes of the lamp due to the action of the reactor II. If the lamp operates properly an electrical discharge will be established between electrodes II and I2, and the voltage drop across these electrodes may be of the order of one-half the voltage appearing acrossthe electrodes prior to the separation of the contacts 24 and 21. Heater 39 is so proportioned that the PR loss therein when the lamp is operating is suflicient to maintain contact arm 23 in its intermediate position so that the contacts 24 and 25 are out of contact respectively with the contacts 21 and 29, thereby maintaining the circuit open at this point. The current can continue to flow from the resistor 3|! through wire 3|, contacts 38 and 39 and wire 4| as above described. *This is the'equilibrium condition for a lamp that is operating properly.

Should the lamp fail to ignite for any reason, as for example if the lamp is defective due to the loss of electron emission from the electrodes H and I2, the transient voltage between these electrodes may initiate a discharge which will not be maintained, or the discharge may not be initiated. Under this condition the high voltage will again be applied to the heater 39 and due to generated heat the cdntact arm 23 will continue to move away from its initial position and toward that position in which an electrical circuit is established between the contacts 25 and 29. Upon closure of the contacts 25 and 29 the electrodes II and I2 will again be energized, the current now flowing from the wire I8 and terminal 28through wire 22,contact arm 23, contacts 25 and 29, contact arm 28, resistor 34 and wire 35 to the wire 3|, from which the remainder of the circuit is as first above described. This just described circuit, as will be observed, is in parallel to the heater 30 and its wire 3|, and as a consequence the FR loss in heater 30 is reduced, causing contact arm 23 to cool and flex toward its original position to interrupt the circuit at the contacts 25, 29. This interruption of the circuit again causes a transient voltage to be applied between the electrodes H and I2 of the lamp, and a further attempted start is made.

If this renewed efiort to start the lamp is in effective, as because the lamp is defective or the discharge cannot otherwise be maintained, reestablishment of the circuit only through heater 30 will again cause contact arm 23 to flex to reengage contacts 25 and 29, and at each opening and closing of the contacts 25 and 29 as just described a new starting impulse will be applied to the lamp.

Also, at each engagement of the contacts 25 and 29 an impulse of current flows through the heater 34 to cause the associated contact arm 28 to flex toward the left as viewed in the drawing. The finger 36 associated with contact arm 28 is of such length and so located with respect to contact arm 49 that after a predetermined number of impulses of current through the heater 34, finger 36 will engage contact arm 40 and flex it to the left, as viewed in the drawing so as to open the circuit at contacts 38 and 39, thus mechanically interrupting the circuit at said contacts. When this circuit is so opened at the contacts 38, 39, current may still flow through the heating element 42 in shunt with the normally closed circuit through the contacts 38 and 39. Under normal operation, when said contacts are in engagement, the amount of current flowing through the heater 42 is insufiicient to cause flexure of the arm 49 sufliciently .to disengage the contacts 38 and 39.- but when the contacts 38 and 39 have been separated by the mechanical operation of the finger 36 all current flowing in the circuit must flow through the heater 42 which, by reason of its association with arm 49, tends to cause-said arm to flex toward the left as viewed in the drawing, so that a position of equilibrium is established by 'said heater 42 wherein the quantity of heat transmitted by the heater 42 to the arm 48 is suificient to hold the arm 48 flexed with its contact 39 separated from the contact 38.

As soon as the contacts 38 and 39 are separated the operation of the starting switch is discontinued, and .when the position of equilibrium of the bimetallic arm 49-is reached owing -to the heat from the resistor 42, the starting switch is locked out of operation owing to the separation of the contacts 38 and 39, current continuing to flow through resistor 38, wire 3 I, wire 43, resistor tact arms 58 and 42 and wire 44, but the quantity of heat involved at heater 38 being only suflicient to hold bimetallicarm 23 in its intermediate sition with its contacts 24 and 25 respectively out of engagement with-contacts 21 and 29, but the heat evolved in the resistor 42 being sufficient to maintain bimetallic arm in its aforesaid open circuit position. This condition will continue until the cause of the difiiculty is removed.

This automatically operating starting switch as described has the advantage that it resets automatically upon deenergizing the circuit. Upon interrupting the inputto the transformer I5, or upon removing lamp ID from its socket, the current through the starting switch is interrupted. Thereupon, the heating elements 38 and 42 cool and reestablish the circuit through contacts 24 and 21, on the one hand,.through contacts 38 and 39, on the other hand, so that the starting switchis restored to its condition for normal operation upon the next energization of the same.

Contact arms 26 and 31 are made of bimetal so as to function as compensation elements responding to the temperature of the ambient. Thus an increase of temperature in the ambient electrode u, wire I8, terminal 20, wire 22, contact arm 23, contacts 24 48, contact arm 54, re-

sistor 52, contact arm 53, wires 54 and 55, con-\ tained between said electrodes. While the lamp is operating the voltage drop across the discharge may, as above noted, be approximately one half of the voltage across these electrodes when no electrical discharge exists, andtherefore, during operation of the lamp, the reduced voltage apwould tend to flex arm 23 to the left as viewed in the drawing irrespective of the operation of heater 38 but arm 26 is so constructed as to compensate for such increase in ambient temperature and retain contacts 24 and 21 in engagement. Similarly arm 31 compensates for the action of the ambient on arm 48.

In the embodiment shown in Fig. 2, wherein the same parts are designated by the same reference characters, bimetallic arm 23 is connected to terminal 28 through wire 22, and carries contacts 24 and 25, but the contacts and 49, which correspond respectively with contacts 21 and 29 in Fig. 1, are fixed relative to each other by con- The electrical circuit through contact arm 58 includes a resistor 52 but, as above indicated, contact 48 maybe made of a-materiai having a, relatively high. resistance so that a separate resistor 52 is unnecessary. The contact arms 58 and 5| are moved as a unit by a bimetallic contact arm 53 which is in circuit with the contact arm 50 and contact 48 but is electrically insulated from the contact arm 5| I and its contact 49. Contact arm 53 is connected by wire 54 to wire 55 leading from resistor 56 which is a heater in heat interchanging relationship with the contact arm 23 and connected at its opposite end to wire 22, so that, as in the embodiment of Fig. 1, the circuit through resistor from said arm 53, resistor 51 being connected to wire 55 by wire 58.

As in the embodiment of Fig. 1, bimetallic contact arm 53 carries, in any suitable way, a

. finger 36, adapted to engage and operate bimetallic contact arm 48 carrying contact 39 which cooperates with contact 38 on a bimetallic contact arm 31 in series with the wire 55. Contact arm 48 is in series with the'wire 4| leading to the terminal 2|, and in shunt around the contactsplied to heater 56 causes a heat dissipation that is sufficient and appropriate to maintain arm 23 flexed with the contacts 24 and 25 thereon intermediate the contacts 48 and 49.

Should the discharge of the lamp not be maintained, the increased voltage is again applied to the heater 56, causingarm 23 to further fleivtoward the left as viewed in the drawings until contact 25 engages contact 49. Thereupon, the current flows from wire 22, through contact arm 23, contacts 25 and 49, contact arm 5|, resistor 51, wire 58 and wire 55. Thereby a shunt circuit is established across the heater 56 which causes said heater to cool and pcrmitthe contact arm 23 to flex toward the right, as viewed in the drawing, to open the circuit at 25, 49. This again gives a transient voltage across the electrodes |2 in a new attempt to initiate the discharge of the lamp. If the lamp does not start, increased voltage is applied to the heater 58, causing contact arm 23 to reestablish a circuit through contacts 25 and 49, and this operation is repeated 1 through a number of cycles.

If the lamp is defective so that a discharge is not sustained between its'electrodes, each closure of the circuit at contacts 25 and 49 causes an impulse of current to flow through the resistor 51, and thereby the bimetallic contact arm 53 becomes progressively heated to cause the same to fiex toward the left as viewed in the drawing. After a predetermined number of actuations the finger 36 engages contact arm 4|] to mechanically open the circuit at thecontacts 38 and 39. The current now flows in increased amount through the resistor 42 to heat the contact arm. 48 and retain the same in its flexed position with the contacts 38 and 39 separated as above described in conjunction with the embodiment of Fig. l. Thereby the operation of the starting switch is discontinued first by the mechanical opening of the contacts 38 and 39 and then by the retention of said contacts in open position by reason of the continued operation of sary when resetting the starting switch to deenergize the starting switch, as by interrupting the current supply through transformer I5 or removing the lamp l8 from its circuit. v

It will therefore be perceived that the present invention provides means for discontinuing the operation of the starting switch of an electrical discharge lamp if the lamp be defective or otherwise fails to start. Said means for discontinuing of transient voltage to the lamp l before the starting switch is rendered inoperative. It will further be perceived that the means provided for discontinuing the operation of the starting switch has the advantage that it is automatically reset to its normal operating condition upon deenergization of the switch, as by interrupting the current supply to the lamp or removing the lamp from the circuit or disconnecting the switch. Furthermore, the invention provides a relatively simple means for effecting the foregoing automatic operations, and one that may be associated with a lamp without unduly complicating the circuits or structure involved. By using a thermally operated switch that remains closed during the normal operation of the circuit and providing means for opening said switch and for energizing electrical means that retain the switch in open position upon the occurrence of abnormal conditions, as evidenced by a failure to start the lamp after a limited number of tries, danger of injury to the starting switch and its transformer, reactor and associated parts has been eliminated in a simple and eflicient way that may be readily embodied in commercial starting switches.

While the embodiments of the invention illustrated on the drawings have been described with considerable particularity, it is to be expressly understood that the invention is not limited thereto as other circuit arrangements, other mechanical means for transmitting movement to or from the thermostatically operated switch, other electrical means energized upon an opening of the switch to retain the latter in its open position, etc., will now readily suggest themselves to those skilled in the art without departing from the principle of this invention. Reference is therefore to be had to the appended claims for a definition of the invention.

What is claimed is:'

1. In a starting switch for electrical discharge lamps of the type having at least two electrodes, on at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contacts in circuit with the electrodes of said lamp and thermally operated means energized by-closing the circuit through said lamp for separating said contacts, a second set of contacts closed by said thermally operated means if the lamp fails to start, said thermally operated means co-operating with said second named contacts to repeat the opening and closing of said circuit through said electrodes for applying a starting voltage thereto, and means; actuated by the repeated operation of said second current only during starting", in combination with normally closed contacts in circuit with the electrodes of said lamp, thermally responsive means for separating said contacts, ah'eating coil energized by completing the circuit through said lamp for actuating said thermally responsive means to separate said contacts and apply a starting voltage to said electrodes, a second set of contacts closed by said thermally responsive means if said lamp fails to start, said thermally responsive means co-operating .with said last named contacts to open and close said circuit alternately and apply repeated starting voltages to said electrodes, a third set of contacts in 'cir-. cuit with said last named contacts and said electrodes,-means mechanically actuated by repeated opening and closing of said second named contacts for openingsaid third named contacts, and means for maintaining said third named contacts in open position.

3. In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contactsin circuit with the electrodes of said lamp. thermally responsive means for separating said contacts, a heating coil energized by completing the circuit through said lamp for actuating said thermally responsive means to separate said contacts and apply a starting voltage to said electrodes, a. second set of contacts closed by said thermally responsive means if said lamp fails to start, said thermally responsive means co-operating with said last named contacts to open and close said circuit alternately said third named contacts, and electrical means energized by the opening of said last named con- 7 tacts for retaining said last named contacts in open position.

4. In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contacts in circuit with the electrodes of said lamp, thermally responsive means for separating said contacts, a heating coil energized by completing the circuit through said lamp for actuating said thermally responsive means to separate said contacts and apply a starting voltage to said electrodes, a second set of contacts closed by said thermally responsive means if said lamp fails to start, said thermally responsive means co-operating with said last named contacts to open and close said circuit alternately and apply repeated starting voltages to said electrodes, a third set of normally closed contacts in circuit with said last named contacts and said electrodes and adapted to be opened mechanically, means actuated by repeated opening and closing of said second named contacts for mechanically opening said third named contacts, and means whereby said third set of contacts is held open only by continuous energization of the starting circuit of said lamp.

5. In a starting switch for electrical discharge lamps of the type having at least two electrodes,

' one at leastof said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contacts in circuit with the elec trodes of said lamp, thermally responsive means for separating said contacts, a heating coil energized by completing the circuit through said lamp for actuating said thermally responsive said electrodes, a thirdset of contacts in series with said electrodes and second named contacts, thermally operated means actuated by the repeated opening and closing of said second named contacts, and mechanical means operated by said last named thermally operated means for separating said third set of contacts.

6. In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contacts in circuit with the electrodes of said lamp, thermally responsive means for separating said contacts, a heating coil energized by completing the circuit through said lamp for actuating said thermally responsive means to separate said contacts.and apply a starting voltage to said electrodes, a second set of contacts closed by said thermally responsive means if said lamp fails to start, said thermally responsive means co-operating with said last named contacts to open and close said circuit alternately and apply repeated starting voltages to said electrodes, a third set of contacts in series with said electrodes and second named contacts, thermally operated means actuated by the repeated opening and closing of said second named contacts, mechanical means operated by said last named thermally operated means for separating said third set of contacts, and electrical means energized by the opening of said last named contacts for retaining said last named contacts in open position.

7. In a starting switch for'electrical discharge lamps of the typehaving at least two electrodes,

one at least of said electrodes being of the filamentary type and requiring an electrode heating current. only during starting, in combination with normally closed contacts in circuit with the electrodes of said lamp, thermally responsive means for separating said contacts, a heating coil energized by completing the circuit through said lamp for actuating said thermally responsive means to separate said contacts and apply a starting voltage to said electrodes, a second set of contacts closed by said thermally responsive means if said lamp fails to start, said thermally responsive means co-operating with said last named contacts to open and close said circuit alternately andapply repeated starting voltages to said electrodes, a third set of contacts in series with said electrodes and second named contacts, thermally operated means actuated by the repeated opening and closing of said second named contacts, mechanical means operated by said last nam'ed thermally operated means for separating said third set of contacts, and thermally responsive means energized by the opening of said third named contacts for maintaining said third named contacts open.

8. In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contacts in circuit with the electrodes of said lamp, thermally responsive means ior separating said contacts, a heating coil energized by completing the circuit through said lamp for actuating said thermally responsive means to separate said contacts and apply a starting voltag to said electrodes, a second set of said third set of contacts, th

contacts closed by said thermally responsive means if said lamp fails to start, said thermally responsive means co-operating with said last named contacts to open and close said circuit alternately and apply repeated starting voltages tosaidelectrodes, a third set of contacts in series with saidelectrodes and second named contacts, thermally operated means actuated by the repeated opening and closing of said second named contacts, mechanical means operated by said last named thermally operated means for separating ermally responsive means carrying one of said third named contacts, and heating means'en'er-gized by-the opening of said third named contacts for retaining said last named thermally responsive means in the position in which said third named contacts are held open.

9. In a starting switch for lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contacts in circuit with the electrodes of the lamp, a bimetallic arm on which one of said contacts is mounted, a resistor in heat interchanging relationship with said arm and energized by the closing of the circuit through said electrodes to effect the fiexure' of said arm and the openingof said contacts to apply a starting voltage to said lamp, a second set of contacts associated with said arm and closed by said arm if said lamp fails to start, said resistor co-operating with said arm to open and close the circuit alternately through said second named contacts a plurality of times if the lamp fails to start, a third set of contacts in circuit with said-second named contacts and said electrodes, a bimetallic arm adapted to actuate said third named contacts, and a heater progressively energized by the opening and closing. of said second named contacts for flexing said last named arm and mechanically opening said third set of contacts.

'10. In a starting switch for electrical discharge lamps of the type having a least two electrodes,

one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contacts in circuit with the elec trodes of the lamp, a bimetallic arm on which one of said contacts is mounted, a resistor in heat interchanging relationship with said arm and energized by the closing of the circuit through said electrodes to effect the flexureof said arm and the opening of said contacts to apply a starting voltage tosaid lamp, a second set of contacts associated with said arm and closed by said'arm if said lamp fails tostart, said resistor co-operating with'said arm to open and clos the circuit alternatelythrough said second named contacts a plurality of times if the lamp fails to start, a third set of contacts in circuit with said second named contactsandsaid electrodes, a bimetallic arm adaptedto actuate electrical discharge I 6 v said third named contacts, a heater progressively energized by the opening and closing of said second named contacts for flexing said last named arm and mechanically opening said third set of contacts, and electrical means energized by the opening of said third contacts for retaining said third contacts in open position.

11. In a starting switch for electrical discharge lamps of the type having at least two electrodes,

one at least of said electrodes being of th filamentary type and requiring an electrode heating current only during starting, in combination with a starting circuit including the electrodes of said lamp and means for alternately opening and closing said circuit to initiate the'operation of said lamp, means for additionally controlling the operation of said starting circuit including additional contacts in circuit with said electrodes, means associated with said first named means for mechanically opening said last named contacts after a predetermined number of operations of said starting circuit at said first named means and means whereby said last named contacts are thereafter closed only upon deenergization of said starting circuit. a

12. In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with a starting circuit including the electrodes of said lamp and thermally operated means for alternately opening and closing said circuit to initiate the operation of said lamp, and thermally responsive means for additionally controlling the operation of said starting circuit including contacts in series with said electrodes and means associated with said first named means for mechanically opening said last named contactsafter a predetermined number of operations of said starting circuit at saidfirst named means and to thereby initiate energization of said second named means to hold said last named contacts in open position.

13. In a starting switch for electrical discharge lamps of the type having at least two electrodes, One at least of said electrodes being of the filamentary type and requiring an electrod heating current only during starting, in combination with contacts in circuit with the electrodes of said lamp and means for alternately opening and closing said circuit to initiate the operation of said lamp, a second set of contacts in circuit with said electrodes, means associated with said first named means for mechanically opening said second set of contacts after a predetermined number of operations of said first named means, and electrical means adapted to maintain said second set of contacts thereafter in open position as long as said starting circuit is energized and to effect reclosure of said second set of contacts only upon deenergization of said lamp.

14. In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrod heating current only during starting, in combination with normally closed contacts in series with the electrodes of said lamp and thermally operated means for alternately opening and closing said circuit to initiate the operation of said lamp, a heating coil for actuating said thermally operated means, a second set of contacts in series with said electrodes, thermally operated means for operating said second set of contacts, a heating coil associated with said second set of contacts, and means associated with one of said first named contactsfor mechanically opening said second set or contacts to initiate energization of said last named heating coil to hold said set of contacts in open position.

15. In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contacts in series with the electrodes of said lamp and thermally operated means energized by closing the circuit through said lamp for separating said contacts, a second set of contacts closed by said thermally operated means if the lamp fails to start, said thermally operated means cooperating with said second named contacts to repeat the opening and closing of said circuit through said electrodes for applying a starting voltage thereto, a third set of contacts in'series with said electrodes, means for opening said third set of contacts, and thermally operated means for holding said third set of contacts open once said contactshave been opened. 4

16. In a starting switch for electrical discharge lamps of the type having at least two electrodes. one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contacts in series with the e1ectrodes of said lamp and thermally operated means energized by closing the circuit through said lamp for separating said contacts, a second set of contacts closed by said thermally operated means cooperating with said second named contacts to repeat the opening and closing of said circuit through said electrodes for applying a starting voltage thereto, a third set of contacts in series with said electrodes, and thermally responsive means cooperating with one ofsaid second set of contacts and actuated by the repeated opening and closing of said second set of contacts for mechanically opening the circuit at said third set of contacts.

17. In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contacts in series with the electrodes of said lamp and thermally operated means energized by closing the circuit through said lamp for separating said contacts, a second set of contacts closed by said thermally operated means if the lamp fails to start, said thermally operated means cooperating with said second named contacts to repeat the opening and closing of said circuit through saidelectrodes for apply ing a starting voltage thereto, a third set of contacts in series with said electrodes, means for opening said third set of contacts, and thermally operated means which ar normally short circuited by said third set of contacts for holding said third set of contacts open. a

18. In a starting switch for electrical discharge lamps of the type having at least two electrodes,

one at least of said electrodes being of the filamentary type and requiring an electrode heating current only during starting, in combination with normally closed contacts in series with the electrode of said lamp and thermally responsive means energized by closing the circuit through said lamp for separating said contacts. a second set of contacts closed by said thermally responsive means it the lamp fails to start, said thermally responsive means cooperating with aid second named contacts to repeat the opening and closing of said circuit through said electrodes for applying a starting voltage thereto, a third set of contacts in series with said electrodes actuated by thermally responsive means, means for opening said third set of contacts, and heating means normally short circuited by said third set oi contacts and comprising a heating coil in series with the electrodes adapted to hold said last named contacts open following opening thereof.

19. In a starting switch for electrical discharge lamps of the type having at least two electrodes, one at least of said electrodes being of the filamental-y type and requiring an electrode heating current only during starting, in combination with normally closed contacts in series with the electrodes of said lamp, thermally responsive means energized by closingthe circuit through said lamp for separating said contacts, a second set of contacts closed by said thermally responsive means if the lamp fails to start, said thermally responsive means cooperating with said second named contacts to repeat the opening and closing of said circuit through said electrodes for applying -a starting voltage thereto, a third set of normaliy closed contacts inseries with said electrodes, thermally responsive means cooperatingtion.

PAUL L. BETZ. 

